Update `README.md` with metadata

This PR updates the metadata in the `README.md` file to include the `license` (MIT inherited from https://github.com/microsoft/dayhoff), `pipeline`, `library`, and `dataset`; which all help with visibility, transparency and discoverability in the Hugging Face Hub.

Note that the paper would be automatically linked when the URL is included within the `README.md`, but at the moment only Arxiv is supported, and given that the paper has been published in bioRxiv it won't be linked yet, but still would be great to include the reference to the paper somewhere in the README.

README.md

@@ -1,5 +1,12 @@
 ---
-{}
+license: mit
+pipeline_tag: text-generation
+library_name: transformers
+tags:
+- protein-generation
+- jamba
+datasets:
+- microsoft/Dayhoff
 ---
 
 # Model Card for Dayhoff